Power supply ripple of the main dipoles and quadrupoles may further limit the dynamic aperture of large proton colliders such as the Large Hadron Collider (LHC) in the presence of the non‐linear field errors of the superconducting magnets. The Super Proton Synchrotron (SPS), the future injector of the LHC, is used to evaluate the effects of power supply ripple. These investigations will allow to specify the quality of the LHC main power supplies. In this report we demonstrate how the ripple spectrum measured at the power supplies of the different SPS magnet chains can be translated into an expected spectrum of tune ripple seen by the beam. To this end the transmission line characteristics of various single elements and magnet chains have been measured and compared to theoretical models. The damping effect of eddy currents induced in the vacuum chamber by the rippled main fields has been measured and compared to a preliminary model. The resulting tune spectrum is then compared with the actual tune ripple that has been measured with the Schottky system. © 1995American Institute of Physics